JPS63164328A - Manufacture of film carrier with bump - Google Patents

Abstract

PURPOSE:To make it possible to make bumps sufficiently thick even though in case where the number of pins is large by a method wherein, after a resist layer is etched to form recessed parts, metal layers are each formed in the recessed parts. CONSTITUTION:A bonding agent layer 11 of a prescribed width is applied on a high- heat resistant base film 10, a conductive sheet 12 is adhered and a substrate 13 is formed. A resist layer 14 is applied on the sheet 12, a pattern film is superposed and ultraviolet rays and an electron beam are irradiated to expose and cure a pattern 14b on the layer 14. This is developed, an electrolytic etching, in which there is little surface roughness, is performed and recessed parts 12a are formed in the sheet 12. An electroforming of gold is performed on non-resist parts 14a and metal layers 15 are grown in the depth direction while their growth in the horizontal direction is suppressed. After the layer 14 is removed with a solvent, a resist layer 16 is formed on the sheet 12. An electroforming of copper is performed on non-resist parts 16a. As metal layers 15 are each buried in the recessed parts 12a and the whole surface is flattened, electroforming metal layers 18 having an enough strength are formed. The metal layers 15 and 18 are transferred on an adhesion layer 21 of a carrier tape 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a film carrier with bumps, in which a large number of leads connected to semiconductor chips such as IC and LSI are supported and arranged on a film.

[Conventional technology]

2. Description of the Related Art Conventionally, metal lead frames have been used to assemble semiconductor devices in which semiconductor chips are integrated with a resin mold and have a large number of protruding vias. Conventional lead frames were formed by punching out thin metal plates with a press or by etching.

By the way, extremely thin fingers (inner leads) are formed on the lead frame, and the tips of the fingers are connected to the electrodes of the semiconductor chip using solder or other means, but the electrodes are generally recessed from their surroundings. It is formed of an aluminum pad or the like. Therefore, the tip of the finger has a bump (
However, as semiconductor devices with a large number of pins are required in recent years, the width of the fingers has to become narrower and narrower, making it difficult to form the bumps mentioned above. There is.

Recently, lead frames using electroforming technology have been developed as a method that eliminates these drawbacks, is easy to manufacture, and allows molding of minute parts.

FIG. 3 is a sectional view for explaining a method of manufacturing a lead frame using electroforming technology previously proposed by the present applicant, and is described in Japanese Patent Application Laid-Open No. 61-234060.

First, as shown in FIG. 3 (al), a resist layer 2 having a desired pattern is formed on the surface of a substrate 1 made of a conductive metal such as stainless steel. The non-resist part 2a, which is a tape-like piece with no resist layer 2 formed thereon, has the same pattern as the shape of the lead frame to be manufactured.Although not shown, there are sprockets at both ends of the substrate 1. A large number of non-resist portions for forming holes are formed at predetermined intervals in a direction perpendicular to the paper surface.

Next, this substrate 1 is subjected to a peeling treatment to activate the surface corresponding to the non-resist portion 2a of the substrate 1, and then, as shown in FIG. The contact material 3 is formed by coating or plating, and then electroforming is performed to form an electroformed metal N4 on the contact material 3, as shown in FIG. 3(C).

A part of the laminated body of the substrate 2 and the metal layer thus formed into a single plate is pressed, and the portion corresponding to the finger 5 is bent as shown in FIG. 5(d). This bent shape is composed of a flat finger base 5a, a raised portion 5b extending obliquely from the finger base 5a, and a tip portion 5C extending parallel from the raised portion 5b.
At the same time, a bump 5d is formed on the lower surface of the tip portion 5c by pressing.

Next, second electroforming is performed to form a new electroformed metal layer 6 on the electroformed metal layer 4, as shown in FIG. 2(e). At this time, the growth rate of the electroformed metal layer 6 is slow because the upright part 5b of the finger 5 is in an inclined position, and the tip part 5c is connected to the upright part 5b by a thin neck, so this part is electroformed. The metal layer 6 grows further, so the finger 5 becomes the tip 5c.

The thickness of the finger base portion 5a and the upright portion 5b are increased in this order.

Finally, when the substrate 1 is peeled off from the contact material 3, as shown in FIG. A lead frame having a bumped finger having a shape as shown in FIG. This is because the surface of the non-resist portion 2a has been subjected to FA release treatment in advance as described above.

Note that the lead frame obtained in this manner is wound up into a roll, for example, and transported and supplied to a manufacturing line for semiconductor devices. Then, using sprocket holes (not shown) formed in the lead frame as a positioning reference, each electrode of the semiconductor chip and the bumps 5d of the fingers 5 are bonded by thermocompression, and the semiconductor device is assembled through the subsequent molding process and lead cutting process. can get.

[Problem that the invention seeks to solve]

According to the manufacturing method proposed by the applicant mentioned above, after forming a recess in the substrate using press working, electroforming is performed on the recess to form fingers with bumps. Compared to the method of forming the entire frame by punching with a press, it is possible to form fingers that are much narrower, and this method is effective for semiconductor devices with a large number of pins.

However, as the number of pins in semiconductor devices continues to increase, the width of the fingers themselves and the pitch between adjacent fingers become narrower. Even if it were possible to form a bump, it would be impossible to form a bump with sufficient thickness.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a film carrier with bumps, which solves the problems of the prior art described above and allows the bumps to be sufficiently thick even when a large number of pins (leads) are used.

[Means for solving problems]

In order to achieve the above object, the present invention includes a step of forming a first resist layer in a predetermined pattern on a substrate whose surface is conductive, and a step of etching the non-resist portion to form a recess in the substrate. forming a first electroformed metal stone to serve as a bump in the recess, and after removing the first resist layer, forming a second resist layer in a predetermined pattern on the substrate surrounding at least the recess. a step of forming a second electroformed metal layer to serve as a lead in the non-resist portion; and a step of peeling off the first and second electroformed metal layers from the substrate. This is a characteristic feature.

[Effect]

According to the above method, the first resist (IJ) on the substrate is etched to form a recess, and then the first electroformed metal layer that becomes a bump is formed in the recess. A bump with sufficient thickness can be molded. Further, after forming the first electroformed metal layer that will become the bump in this way, a second resist layer is formed on the substrate, and a second electroformed metal layer that will become the lead is formed in the non-resist part. Since the leads can be formed into fine patterns, it is therefore possible to manufacture a film carrier with bumps that can form bumps at the tips with sufficient thickness even when the number of leads increases. can.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figures 1 (a) to (f) are perspective views showing the manufacturing process of a film carrier with bumps according to an embodiment of the present invention, and Figures 2 (a) to (f) correspond to each process in Figure 1. FIG.

First, as shown in Figure 1 (111) and Figure 2 (a),
After applying an adhesive layer 11 to a predetermined width on a highly heat-resistant base film 10 such as polyimide, a conductive sheet 12 made of a thin stainless steel plate is adhered onto the adhesive layer 11, thereby imparting conductivity to the surface. A stained substrate (3) is formed. This base film 10 has the same width as a carrier tape to be described later, and sprocket holes 10a are formed at regular intervals along both side edges. It is also possible to use a metal other than stainless steel, such as nickel, as the conductive sheet 12, but in this case, the surface must be subjected to a peeling treatment using anodizing, selenite, chromic acid, or the like.

Next, as shown in FIGS. 1(b) and 2(b), a first resist layer 14 made of a photoresist material is applied onto the conductive sheet 12 of the substrate 13, and sprocket holes 10 are formed on the first resist layer 14.
After overlapping a pattern film (not shown) using a pattern film, ultraviolet rays and electron beams are irradiated through the pattern film to form a pattern 14b (excluding non-resist areas 14a) on the first resist layer 14. Exposure and harden. The thickness of this first resist layer 14 is approximately 4 μm.

This is further developed and subjected to chemical etching or electrolytic etching such as electrolytic grinding, preferably electrolytic etching with less surface roughening, to form recesses 12a in the conductive sheet 12 corresponding to the non-resist portions 14a. The recesses 12a are for forming bumps, and by controlling the etching conditions, a fine pattern with sufficient depth (20 to 40 pm thick) can be realized.

Next, the substrate 10 on which the first resist layer 14 has been formed is sent to electrolysis (not shown), and as shown in FIG. 1(C) and FIG. Casting is performed to form a first electroformed metal layer 15 slightly thinner than the first resist layer 14 in the non-resist portion 14 . In this case, as described above, since the film thickness of the first resist Jii 14 is as thin as about 4 μm, it is possible to grow the first electroformed metal [15 in the depth direction while suppressing the growth in the horizontal direction. A sufficiently thick first electroformed metal layer 15 for forming bumps is formed in the non-resist portion 14a of the resist layer 14.

Next, as shown in FIG. 1 (dl) and FIG. 2 (d), after removing the first resist layer 14 with a solvent such as acetone or methylene chloride, a heat-sensitive material is placed on the conductive sheet 12 of the substrate 13. A second resist layer 16 is formed using the following method.The film thickness of this second resist layer 16 is approximately 15 to 40 μm.
It is preferably about 30 μm, which is sufficiently thicker than the first resist layer 14, and is formed by a dry film having the above thickness or by multiple coatings. Then, another pattern film (not shown) is superimposed on the second resist layer using the sprocket hole 10a again, and then the pattern film is irradiated with ultraviolet rays and electron beams to form the second resist layer 16. A predetermined non-registration portion 16a
form. This non-resist portion 16a has the same pattern as the lead frame to be manufactured, and although only the fingers are shown in FIG. 1 to simplify the explanation, in reality, outer leads, frame portions, etc. are formed. (However, no sprocket is formed on the lead frame, and no pattern for that purpose is formed.)

- Next, as shown in FIG. 1(e), the substrate 13 with the second resist layer 16 formed thereon is sent to the electrolytic bath 17, and
As shown in e), the non-resist portion 16a is electroformed using copper, and the second electroformed metal layer 18 is formed on the non-resist portion 16a.
is formed to be slightly thicker than the second resist layer 16. In this case, the bottom surface of the non-resist portion 16a is located inside the recess 12a.
Since the electroformed metal layer 15 is buried and flattened,
The second electroformed metal JilB grows to a uniform thickness along the pattern of the second resist layer 16, and a second electroformed metal layer 18 having sufficient mechanical strength is formed. In this way, the non-resist portion shown in FIG. 2(e) has a bump (
A finger (second electroformed metal N18) having a second electroformed metal layer 15) is formed, and a lead frame having a predetermined shape made of the electroformed metal layer as a whole is formed.

Finally, as shown in FIG. 1(f), a carrier tape 19 made of polyimide or the like has the same width as the base film 10 and sprocket holes 19a are formed at regular intervals along both ends.
and the substrate 13, which is in the process shown in FIG.
f), the first and second electroformed metals 711
5.18 is transferred onto the adhesive layer 21 of the carrier chip 119.

Specifically, the sprocket holes 10a and 19a of the substrate 13 and the carrier tape 19 are used to stack the substrate 13 and the carrier tape 19 between pressure rollers 20 and 20 heated by a heater (not shown) and feed them. Both are conveyed at a constant speed and pressed between the pressure rollers 20.20, so that only the first and second electroformed metals 115.18 formed on the conductive sheet 12 with good releasability are integrated. The second resist layer 16 remains on the substrate 13 side.

By going through the above steps, the carrier tape 19
First and second electroformed metals on top? ! A lead frame consisting of 15.18 is transferred to obtain a bumped film carrier. This film carrier is wound up into a roll, for example, and transported and supplied to a manufacturing line for semiconductor devices, and the fingers (second electroformed metal layer 18 ) The bump at the tip (first electroformed metal layer 15) is thermocompression bonded to each electrode of the semiconductor chip, and a semiconductor device is obtained through the subsequent molding process and lead cutting process.

In the above embodiment, the first electroformed metal layer 15 for forming bumps is made of gold, which has good peelability from stainless steel (conductive sheet 12), and the second electroformed metal layer 18 for forming fingers is made of gold. Since copper is used, which has good adhesion to gold and is easily peeled from stainless steel, the lead frame on the substrate 13 can be easily transferred onto the carrier tape 19. Furthermore, no sprocket holes are formed in the lead frame composed of the first and second electroformed metal layers 15.18, but sprocket holes 19a are formed in the carrier tape 19 on the side to which the lead frame is transferred. Therefore, it is possible to reduce costs by reducing the number of electroformed parts as much as possible.

〔Effect of the invention〕

As described in detail above, according to the present invention, after a recess is formed in a substrate by an etching technique, the first electroformed metal layer that becomes a bump is formed in the recess. Not only can bumps with sufficient thickness be realized, but also the second electroformed metal layer, which will become the fingers, is formed on the portion flattened by the first electroformed metal layer, so the leads including the fingers can also be made fine. It is possible to provide a film carrier with bumps that can be formed into a pattern with sufficient thickness, and can therefore be made into a large number of bottles (leads) without impairing the thickness of the bumps.

[Brief explanation of the drawing]

Figure 1 (a), (b), (cl, (di, (e)
), (r) is a perspective view showing the manufacturing process of a film carrier according to an embodiment of the present invention, FIGS. 2(a), (b),
(cl, (di, (e), (f) are sectional views of main parts corresponding to each process in Fig. 1, Fig. 3 (a), (b),
(C1゜(d), (8), and (f) are main part sectional views showing the conventional lead frame manufacturing process. 10...Base film, 10a...Sprocket hole, 11...Adhesion agent layer, 12... conductive sheet, 12
a... Concave portion, 13... Substrate, 14... First resist layer, 14a... Non-resist part, 15... First electroformed metal layer, 16... Second resist Layer, 16a...
- Non-resist part, 17... Electrolytic bath, 18... Second electroformed metal layer, 19... Carrier tape, 19a...
Sprocket hole, 20... Pressure roller, 21... Adhesive layer. Figure 1 l la 12 Figure 1 Figure 2 Figure 3 υσ 5b

Claims (2)

[Claims] (1) A step of forming a first resist layer in a predetermined pattern on a substrate whose surface is made conductive, a step of etching the non-resist part to form a recess in the substrate, and a step of forming a first resist layer to become a bump in the recess. forming a second resist layer in a predetermined pattern on the substrate surrounding at least the recessed portion after removing the first resist layer; The second lead to
A method for producing a film carrier with bumps, comprising: forming an electroformed metal layer; and peeling off the first and second electroformed metal layers from the substrate. (2) A method for manufacturing a bumped film carrier according to claim (1), wherein the second resist layer is formed to be thicker than the first resist layer.